A NBW METHOD OF GRADING 
MILK AND CREAM. 
By Wm.C. Wood ward. 



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UNITED STATES PUBLIC HEALTH SERVICE 



A NEW METHOD OF GRADING 
MILK AND CREAM 



BY 



WM. C. WOODWARD 

Health Officer, District of Columbia 



REPRINT No. 117 

FROM 

PUBLIC HEALTH REPORTS 

February 21 1913 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1913 



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D. Of- D. 
MAR 29 W3 



A NEW METHOD OF GRADING MILK AND CREAM. 1 

By Wh. C. Woodward, Health Officer, District of Columbia. 

That the score card has been of service in the improvement of 
sanitary conditions on dairy farms, possibly few will deny. It has 
failed, however, with respect to one most important feature of milk 
control inasmuch as it does not afford a sufficient basis upon which 
to found an opinion as to the wholesomeness and nutritive value 
of milk as it reaches the consumer. And if the scores of dairy farms 
give but an imperfect idea of the quality of the milk as it reaches 
the consumer, an attempted study of a series of scores of dairy farms 
and milk shops, chemical analyses and bacteriological analyses leaves 
the inquirer who is not technically skilled with respect to the matter 
in a dazed and quite helpless condition. In order to enable the 
consumer to determine the. quality of the milk he is purchasing, the 
health department of the District of Columbia has devised a method 
for grading the finished product. 

Essentials of the grading of milk. — Any ideal system of grading 
milk as delivered to the consumer must take into consideration 
the condition of all of the farms from which milk is or is liable to be 
derived, the condition of the milk shop from which it is distributed, 
the chemical analysis of the milk, and the bacteriological analysis. 
The result must be expressed in a manner easily understood by the 
public and in a way that will afford ready and fair comparison between 
milk from any number of sources. 

Method of grading. — The method of grading milk adopted by the 
health department of the District of Columbia is as follows : 100 points 
are allowed for the dairy farm, both equipment and management; 100 
points are allowed for the cattle; 100 points are allowed for the milk- 
distributing station, if the milk is not distributed directly from the 
farm; 100 points are allowed for the chemical analysis; and 200 points 
are allowed for the bacteriological examination. The total number 
of possible points is 600 if there be a milk-distributing station, and 500 
if there be no such station. By dividing the total number of points 
allowed by the total number of points possible a figure is obtained in 
the form of a decimal fraction representing the grade of the milk. 
Any unusual conditions bearing upon the nutritive quality of the 
milk or on its wholesomeness, but not susceptible of being reduced to a 

1 Reprint from the Public Health Reports, Vol. XXVIII, No. 8, February 21, 1913. 
80926°— 13 (3) 



percentage basis, are to be set forth in an explanatory note, if the grade 
is computed during the continuance of such conditions; such, for 
instance, as a milk-borne outbreak of typhoid fever or other conta- 
gious disease. 

Bating the cattle. — For a number of years past the health depart- 
ment of the District of Columbia has scored health and cleanliness of 
cattle independently of the general score for management and equip- 
ment of the dairy farm, allowing 100 points for each. It has seemed 
to the department that under the method of scoring ordinarily 
adopted, enough weight is not allowed for the health of cattle nor 
enough latitude for variations in their healthfulness and cleanliness. 
But while the system of scoring cattle independently of farm manage- 
ment and equipment facilitates the scoring of milk in the manner 
herein described, yet with a simple mathematical adjustment the 
method can be used anywhere. 

When the milk distributed through a given establishment comes 
from but one farm, the determination of the rating to be assigned to 
the cattle is a simple matter, requiring merely the finding of the aver- 
age of the scores given the cattle at a series of inspections by the 
dairy-farm inspectors. But in every large milk-distributing estab- 
lishment the milk comes from many farms, and these farms vary 
widely in the number and condition of the cattle maintained for 
dairy purposes. The milk distributed from such an establishment 
is a composite of the milk from all of the contributing farms. The 
influence of each farm on the composite mixture, however, is not 
equal, but depends upon the proportion and quality of the milk it 
contributes as compared with the whole output. For practical pur- 
poses the proportion of milk supplied may be regarded as deter- 
mined by the number of cows maintained. The method adopted, 
therefore, allows weight to the score for each dairy herd proportion- 
ate to the number of cattle it contains. The score for the herd on 
each farm is multiplied by the number of cattle in it. The total 
number of cattle in all contributing herds is learned by reference to 
the dairy-farm records. Then all of the scores, multiplied as above 
described, are added, and the sum thus obtained is divided by the 
total number of cattle. The quotient is the rating for the cattle. 

The method may best be understood by a simple illustration. 
Producers A, B, and C all send their milk to Dairy No. 342. A has 
100 cows, scored 100. B has 50 cows, scored 80. C has 10. cows, 
scored 40. To determine the rating to be allowed for the cattle in 
computing the final score: 

Producer. 

A (number of cattle) 100 (multiplied by score) 100=10, 000 

B (number of cattle) 50 (multiplied by score) 80= 4, 000 

C (number of cattle) 10 (multiplied by score) 40= 400 

160 14, 400 



Dividing the sum of the multiplied score, 14,400, by the total number 
of cattle, 160, the quotient is 90, the rating to be allowed for the cattle 
in determining the grade of milk distributed by the common 
distributing agency, Dairy No. 342. 

The significance of the method is best understood by supposing 
that the 100 cows on the farm of A were scored 40 instead of 100 and 
the 10 cows on the farm of C were scored 100 instead of 40, the score 
for B's herd remaining the same. The resulting rating would then 
be as follows, notwithstanding the fact that the milk would still come 
from exactly the same number of cows, on the same farms, with the 
same ratings, viz, 40, 80, and 100. 

Producer. 

A (number of cattle) 100 (multiplied by score) 40=4,000 

B (number of cattle) 50 (multiplied by score) 80=4, 000 

C (number of cattle) 10 (multiplied by score) 100=1, 000 

160 9, 000 

Dividing the sum of the multiplied scores, 9,000, by the total number 
of cattle, 160, the quotient is 56.25, the rating for the cattle in 
determining the grade of the composite milk output. 

If the simple method of averaging the scores of all herds without 
reference to the number of cattle in each had been adopted, the rating 
would have been the same in each instance: (Score 100, plus score 80, 
plus score 40) divided by the number of herds, 3, equals 73.33. 

The method of rating the cattle has been described at some length 
and enlarged upon by illustrations in order that it may be made per- 
fectly clear. The elaboration may possibly have served to convey the 
impression that the method is complicated, but a few minutes' study 
of it will show that such is not the case. The application of the 
method to any considerable number of dairy-herd ratings will, how- 
ever, certainly be tedious unless the records have been kept especially 
for the purpose of facilitating such computations. This department 
has devised a system of record keeping, illustrated in the table on 
page , that is expected to facilitate the making of such computa- 
tions in the future. In the meantime, in determining the rating of 
the cattle furnishing milk to any particular distributing establishment, 
the department will not undertake to consider the score for every 
dairy farm but only for a number representing a fair average, say five, 
selected at random. 

If on any farm a substantially new herd is obtained, as when a herd 
is tuberculin-tested and all " reactors" are eliminated from it, the 
rating for dairy cattle is based solely on scores for the new or reno- 
vated herd. 

Rating of the dairy farm. — What has been said with reference to 
the determination of the rating to be assigned to the cattle applies 
with equal force to the determination of the rating for the equipment 



6 

and management of the dairy farm. Due weight must be allowed 
for the amount of milk that each farm supplies, and this can be done 
in the same way as weight is allowed for the score for health and 
cleanliness of cattle, pointed out in the preceding paragraphs. 

Rating of dairies. — The term " dairy" in the District of Columbia 
is regarded as meaning merely the place from which the milk is dis- 
tributed within the city. As every establishment is scored on the 
basis of 100, it is necessary merely to take a number of scores of 
the dairy under consideration sufficient to be fairly representative, 
say three, and to find the average. 

Rating of chemical analyses. — The value of the chemical analysis of 
milk lies in the fact that it shows the food value. Cases of deliberate 
watering are in this jurisdiction rare, and the use of preservatives and 
coloring matter is practically unknown. In order that the results of 
chemical analyses may be used in the grading of the milk, it is neces- 
sary to reduce them to a scale, with 100 as a maximum. As the 
nutritive value of milk is determined by the total solids, the scale 
adopted by the health department is based upon the percentage of 
total solids and not upon the fat. The scale is as follows: 

Scheme/or rating chemical analyses. 
Total solids: Rating. 

11 per cent or less 

More than 11 per cent but not more than 12 per cent 40 

More than 12 per cent but not more than 12.50 per cent 60 

More than 12.50 per cent but not more than 12.75 per cent 70 

More than 12.75 per cent but not more than 13 per cent 80 

More. than 13 per cent but not more than 13.25 per cent 90 

More than 13.25 per cent 100 

If any sample contains added water, deduct 40 points. For milk 
containing preservatives of any sort deduct the entire chemical 
rating, and give zero for the bacteriological rating immediately 
preceding the finding of the preservatives. The average rating of not 
less than three consecutive analyses is to be taken. 

Rating of oacteriological analysis. — In determining the grade of 
the milk as sold, 200 points are allowed for bacteriological analysis. 
As some bacteria are found in all milk in the ordinary channels of 
trade and may, therefore, be looked upon as commercially normal, 
the primary rating takes into consideration merely the total bacterial 
count. Bacilli of the colon group and streptococci are, however, 
looked upon as foreign to wholesome milk, and for their presence 
certain deductions are made from the rating allowed on the basis of 
the total bacterial count alone. The remainder represents the 
absolute rating for the bacteriological examination of the milk. 
The standards adopted are as follows: 



Rating for bacteriological findings. 



Raw milk. 



Pasteurized milk. 



Points 
allowed. 



5,000,000 and upward 

4,000,000 to 5,000,000 

3,000,000 to 4,000,000 

2,000,000 to 3,000,000 

1,000,000 to 2,000,000 

500,000 to 1 ,000,000 

400,000 to 500,000 

300,000 to 400,000 

200,000 to 300,000 

100,000 to 200,000 

50,000 to 100,000 

25,000 to 50,000 

10,000 to 25,000 

Less than 10,000 

For the first 1,000 colonies of the colon group or streptococci, 
whichever may be the more numerous, deduct 20 points and 
deduct 10 points for each subsequent 1,000. 



100,000 and upward 

90,000 to 100,000 

80,000 to 90,000 

70,000 to 80,000 

60,000 to 70,000 

50,000 to 60,000 

40,000 to 50,000 

35,000 to 40,000 

30,000 to 35,000 

25 ,000 to 30,000 

20,000 to 25,000 

15,000 to 20,000 

10,000 to 15,000 

Less than 10,000 

For the first 100 colonies 
of the colon group or strep- 
tococci, whichever may be 
the more numerous, deduct 
10 points, and deduct 2 
points for each subsequent 
100. 




20 
40 

60 
80 
100 
120 
140 
1C0 
170 
ISO 
190 
195 
200 



It will be noted that the foregoing plan for the evaluation of the 
bacteriological findings lays down a basis for raw milk different from 
that for pasteurized milk. This is undoubtedly fair when the ratings 
of two or more samples of milk of the same class are to be compared, 
but it would be manifestly unjust to compare such a rating of raw milk 
with a rating of pasteurized milk unless this difference were taken 
into consideration. In order to prevent such unfair comparisons, 
ratings for pasteurized milk should be accompanied always by some 
descriptive term, say the word "pasteurized," and if it be desired 
to compare the ratings of pasteurized milk with a rating of raw 
milk, both should be scored on the same basis, preferably that for 
raw milk. 

Hypothetical cases may easily be conceived in which the scales 
laid down above would give figures manifestly misleading, and 
possibly such cases may be found in practice. Such would be a 
case in which the colonies of the colon group or the streptococci 
were numerous while the general bacterial count was very low. A 
fair examination of a reasonable number of entries in the records of 
this department, however, failed to reveal any instances of this kind. 

In any case the average rating of not less than three consecutive 
analyses is to be taken. 



8 

Examples. — As an illustration of the way in which the method of 
scoring described above works out in practice, the following examples 
are given from the records of this department : 

Health Department of the District of Columbia — Dairy record. 

DAIRY NO. 1. LICENSEE: JOHN DOE. RAW MILK. 





Dairy farm. 


Dairy 
score. 


Chemical 
analysis. 


Bacteriological analysis. 




Date. 


d 

a 

03 
ft 


_oj 

d 


<B 

O 
U 

a> 
O 


%-, 

o 
o 

a 

u 
03 
ft 


2 
o 


si 

.9 

<A 


o 
o 


d 

"o 

O 


Streptococci. 
Rating. 


Remarks. 


1912. 
Apr. 27 












13.32 


100 








May 29 


934 


200 


100 


99.3 










Oct. 9 


86.61 
84.68 






:::::::::::.: 








Nov. 7 






















Nov. 25 














2,100 








200 




Dec. 7... 


934 


160 


100 


98.0 








Dec. 21 




::::::: ::::::: 




5,000 








200 




1913. 


934 


150 


100 




98.5 










Jan. 11 


86.21 














Jan. 14. . 










13.54 
13.32 


100 
100 












Jan. 14. . 






















Jan. 31. 












2,800 








200 






















Ratings for milk Feb. 10. 






100 


98.6 


85.2 




100 








200 



















Grade for output of Dairy No. 1, John Doe, proprietor, 97.3. 

Note.— This is the grading for a special milk, sold for more than twice as much as ordinary market milk. \ 
DAIRY NO. 2. LICENSEE: RICHARD ROE. PASTEURIZED MILK. 



1912. 
July 11 


1327 
1764 


63 
40 


70 
100 


68.2 
84 
















Sept. 19 
















Oct. 11 


99.85 
99.63 














Nov.12 
























Nov. 12 










13.32 
13.08 


100 
90 












Nov.13 






















Dec. 4 


4945 
383 


15 

21 


70 
67 


68.0 
60.5 














Dec. 24 


















1913. 
Jan. 3 








21,000 
5,000 


200 



100 



168 
200 




Jan. 14 


















Jan. 15 










99.78 








Jan. 19 














3,000 








200 




Jan. 24 


763 


29 


66 


41.7 










Jan. 30 




13.17 


90 


































Ratings for milk Feb. 10. 






75.4 


66.4 


99.7 




93.3 








189.3 



















Grade for pasteurized milk sold by Dairy No. 2, Richard Roe, proprietor, 85. 

Rating of cream. — While no chemical or bacteriological standards 
have been laid down for cream and other milk products, the method 
of grading described above may readily be applied to them, proper 
scales being first established for chemical and bacteriological data. 

Conclusions. — The method of determining the nutritive value of 
milk and its wholesomeness and of expressing them in a single figure, 
as described in this article, is not perfect or final; it will be improved 



as the result of the future experience of the writer and of others. It 
is believed, however, to mark an advance in the supervision and 
control of the milk supply in that it enables the supervising officer to 
give to an}' consumer definite and easily understandable information 
as to the relative nutritive value and wholesomeness of milk from 
different sources in the very form in which the milk from each may 
be expected to reach the consumer. The method is applicable to 
any grade of milk, from certified milk to "cooking" milk, and prices 
may be fixed according to the grade of the milk furnished, without 
any formal "certification" as the term is now understood, and with- 
out any official "classification." 

As the method of scoring herein proposed becomes familiar to the 
consuming public, of all milk selling at a given price that milk will 
be most hi demand which has the highest rating, and if circumstances 
make it expedient to increase the price of milk, a dealer, if his milk has 
a high grade, can logically refer to that fact in justification of the 
increase. To every dealer who desires to increase his business and 
to every dealer who wants to raise his price — and this would seem to 
include all dealers whatsoever — a high grading of his output becomes 
of commercial value. Clearly, however, in order to obtain a high 
grading for his milk as he delivers it to the consumer the dealer will 
not only have to see that the milk is carefully handled after it comes 
into his possession, but will have to obtain it in the first instance from 
farms that score high. The dealer, therefore, will have to keep in 
closer touch than heretofore with farms that produce milk for him. 
A good farm score becomes then also of commercial value, since such 
a score sustains the grade of the milk as delivered, while a low farm 
score pulls it down; and it becomes of more interest to the farmer 
than it now is to conduct his farm in such a manner as to obtain the 
highest score possible. 

The method of grading milk herein proposed reduces to a minimum 
the influence of the personal equation. The scoring of a single farm 
by the same dairy farm inspector at different times or, as will most 
commonly be the case, the scoring of different farms by different 
inspectors at different times, and the scoring of the dairy or milk 
shop at still different times and by other inspectors, will reduce the 
personal equation very much; and with respect to all, except pos- 
sibly the very last score, that will be taken into consideration when 
any given milk grade is computed, the interested farmer or milk 
dealer will have opportunity to appeal from the inspector to the 
higher supervising officer before the score enters into the grading. 
Chemical analyses will, moreover, presumably be made by one person 
and bacteriological examinations by another, and as three or more of 
each of these will enter into the final grading, it may be possible 
even that two or more chemists and two or more bacteriologists will 



10 

participate in the work. Certainly, then, personality can have but 
a minimum influence in determining the final grade — that is, if we 
except the influence of the personality of the milk producer and the 
milk dealer in each conducting his business as it should be conducted. 

As the records of the department have not been arranged with a 
view to the grading of milk in the manner proposed in this article, the 
computing of milk grades will for a time be troublesome. The 
rearrangement of the system of record keeping in such a manner as 
to facilitate in the future the computation of milk grades will involve, 
however, no great difficulty. A tentative arrangement is shown in 
the specimen gradings which appear on page 338, figures from actual 
records having been transferred to the form of record which it is 
proposed to keep. Figures are to be entered on such a proposed 
record daily as they come in from the inspectors and from the labora- 
tories, but it will be necessary to compute ratings for the milk only 
when request is made, or otherwise at stated intervals, say monthly, 
or quarterly. The results of such periodical computations should be 
communicated to the milk dealer primarily interested, for his infor- 
mation and guidance, and such a course will be followed if clerical 
assistance be available for that purpose. 

While the grading of milk in the manner described in this article 
will consume some time and, therefore, add to the cost of the milk 
inspection service, it will make of practical value many reports and 
figures now collected at a considerable cost, and then buried in the 
official records without affording a basis for intelligent action by the 
milk supervising authority or, what is even more important, for 
intelligent action by the consuming public, which, after all, is in 
supreme control of the milk situation. 

o 



6AYL0RD BROS. 

MAKERS 

SYRACUSE, ■ MY. 

PAT. JAN. Zl, I9Q8 




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